Academics

Xuesheng Chen

Professor of Physics

Degrees

Ph.D., M.S., Boston College
B.S., University of Science and Technology of China

Research Interests

Novel ceramic materials for microchip and high power ceramic lasers:

Ceramic laser materials have recently received a lot of attentions because they are potentially great candidates for high-efficiency microchip or high power lasers. Contrast to popular single-crystal laser materials such as the rare-earth ion Nd doped single crystal YAG, ceramic materials are easy to be fabricated into large size and can accommodate high rare-earth ion (laser ion) concentrations. The first ceramic laser output was obtained in 1995 in Nd:YAG, and the first Yb:Y2O3 ceramic laser was just demonstrated in April 2003. To make ceramic lasers possible, the ceramic materials have to be made highly transparent with very low porosity and scattering loss. Recently, my students and I are working on a new kind of transparent ceramic materials, for example: Er-doped Pb-La-Zr-Ti-O (PLZT), for possible high-efficiency microchip or high-power laser applications. We concentrate on optical studies of this newly developed rare-earth ion doped PLZT and other lead-based ceramic materials. Our studies can provide crucial information for promising applications in new optical devices including PLZT ceramic lasers. This research has being supported by National Science Foundation and Wheaton Research Partnership Program

Rare-earth ion doped laser crystals:

The most prominent rare earth ion in laser applications is trivalent neodymium (Nd) ion, which yields strong emission at wavelengths around 0.9, 1.0 and 1.3 micon when doped in a variety of hosts. Crystals with garnet structure are popular laser hosts for Nd ions. For example, the single crystal Nd:YAG has served over forty years as the most important solid-state laser material. Fluoride crystals are also found to be good hosts for Nd ions such as Nd:YLF. The Nd lasers have found many important applications such as laser radar and remote sensing. One of the recent efforts in NASA is to develop Nd laser systems that can produce a laser line at 0.94 micron for remote sensing of water vapor (H2O) in the atmosphere because water has a strong absorption line right at 0.94 micron. It is crucial to know how the Nd line positions and widths change with the host and temperature for efficient and effective Nd laser applications. The work on Nd doped laser crystals is to investigate thermal line position tuning (shift) and broadening of the Nd luminescence lines in different host crystals, focusing on garnet and fluoride hosts. Most of the crystals used in the study were provided by NASA.

Upconversion energy transfer processes in laser materials:

Upconversion phenomena have been studied actively in rare-earth ion doped laser solids. Typical rare-earth ions that are good for upconversion are Er, Tm, Ho, Pr, and Nd ions. The rare-earth ion Yb is often co-doped with some of these ions because it can help absorb energy efficiently and enhance the upconversion process. One of the most important applications of upconversion is to make upconversion lasers, which generally emit light that has higher photon energy than the pump photon energy. The research is to study the temperature and concentration dependence of upconversion processes in rare-earth ion doped laser solids, including single crystals and ceramics.

Experimental

My research involves intensive experimental work, including the measurement of photoluminescence, absorption, transmission, reflectance, excitation, and lifetime over a wide range of temperatures. Measurement equipment includes lasers and other light sources from UV to IR, monochromators, spectrographs, light detectors, electronics, and computer date acquisition system.

Research Grants

My research has been supported by National Science Foundation, NASA, Air Force Office of Scientific Research, Research Corporation, Wheaton College, as well as industrial partners.

Charlotte Wong '05 and Xuesheng Chen, "Concentration Dependence of Transmission of Er-doped Laser Crystals," presented at The 2002 Fall Meeting of New England Section of American Physical Socity, 25-27 October 2002, Bridgewater State College, Bridgewater, MA.

Leanne Lortie '06 and Xuesheng Chen, "Absorption Studies of the Er Ion Doped PLMNT and PLZT," presented at the 2002 Fall Meeting of New England Section of American Physical Socity, 25-27 October 2002, Bridgewater State College, Bridgewater, MA.

Xuesheng Chen, "Thermal Tuning and Broadening of the Spectral Lines in Nd Laser Crystals," a lecture given at the International School of Atomic and Molecular Spectroscopy - Workshop on The Status and Prospects of Luminescence Research, Erice-Sicily, Italy, 7-13 July 2002.

Xuesheng Chen, "Concentration and Temperature Dependence of Basic Luminescence Processes," a lecture given at the International School of Atomic and Molecular Spectroscopy: Spectroscopy of Systems with Specially Confined Structures. Erice-Sicily, Italy, June 15-30, 2001.

B. Di Bartolo and Xuesheng Chen, "Thermal Effects on the Spectral Characteristics of Laser Solids," a talk given at the 198th Meeting of The Electrochemical Society, 22-27 October 2000, Phoenix, Arizona, USA.

Xuesheng Chen and B. Di Bartolo, "Thermal Effects on Rare-Earth Spectra in Solids," a lecture given at the International School of Atomic and Molecular Spectroscopy, 13th Workshop: Advanced Topics in Luminescence Spectroscopy, 23-29 July 2000, Erice, Sicily, Italy.

Xuesheng Chen and B. Di Bartolo, "Temperature Effects on the Spectra of Nd-doped Crystals," a lecture given at the 2nd International Symposium on Laser, Scitillator and Nonlinear Optical Materials ˙ã Photonic Materials for the 21st Century, May 28-31, 2000, Lyon, France.

Liberty Gunter '00, Carol McGeoch '01, and Xuesheng Chen, "Spectroscopic Studies on the Erbium-doped Laser Materials YSGG:Er and GGG:Er at Different Temperatures," presented at the 2000 Spring Meeting of the New England Section of American Physical Society, April 14-15, 2000, Rhode Island College, Providence, RI,

Xuesheng Chen and B. Di Bartolo, "Thermal Effects on the Spectra of Rare Earth Ions in Solids," a talk given at the 30th Winter Colloquium on the Physics of Quantum Electronics. January 9-12,2000, Snowbird, Utah.

Xuesheng Chen and B. DiBartolo, "Effects of the Ion-Phonon Interaction on Line Broadening and Shift in Rare-Earth-Ion Doped Laser Crystals," a talk given at the International Workshop on Advances on Solid State Luminescence Spectroscopy, Erice, Italy, 22-28 June 1998.

Timothy Nguyen '00*, Qui Luu '00* and Xuesheng Chen, "Optical Properties and Upconversion Luminescence of Er3+ Doped GGG Laser Crystals," the 1998 New England Section Meeting of the American Physical Society, 3-4 April 1998, Clark University, MA; the abstract was published in Bulletin of the American Physical Society, Vol.48, April 1998.

Qui Luu '00*, Timothy Nguyen '00* and Xuesheng Chen, "Luminescence of YSGG:Er3+ at Two Different Erbium Concentrations," the Spring 1998 New England Section Meeting of the American Physical Society, April 3-4, 1998, Clark University, MA; the abstract was published in Bulletin of the American Physical Society, Vol.48, April 1998.

Xuesheng Chen, B.DiBartolo and John Collins, "Temperature Dependence of Near Infrared to Visible Upconversion Luminescence of Er3+ in YSGG," in Ultrafast Dynamics of Quantum System:Physical Processes and Spectroscopy Techniques, Proceedings of a NATO Advanced Study Institute, Erice, Sicily, 15-30 June 1997, published by Plenum Press, New York, 1998.

Xuesheng Chen, John Collins and B. Di Bartolo, "Observation of the Blue Shift with Increasing Temperature of the R1-Z5 Line Position of Nd3+ in Garnet Laser Crystals," Bulletin of the American Physical Society, Vol. 38, 1993.

Xuesheng Chen and B. Di Bartolo, "Thermal Behavior of Spectral Line Positions and Widths of Nd3+ in GSGG," in Optical Properties of Excited States in Solids, Proceedings of a NATO Advanced Study Institute held in 16-30 June 16-30, Plenum Press, New York, 1992, p699.